libctf: error-handling fixes

libctf: error-handling fixes

libctf/ChangeLog
2020-11-20  Nick Alcock  <nick.alcock@oracle.com>

	* ctf-create.c (ctf_dtd_insert): Set ENOMEM on the dict if out of memory.
	(ctf_dvd_insert): Likewise.
	(ctf_add_function): Report ECTF_RDONLY if this dict is not writable.
	* ctf-subr.c (ctf_err_warn): Only debug-dump passed-in warnings if
	the passed-in error code is nonzero: the error on the dict for
	warnings may relate to a previous error.